GCSE CS Programming

GCSE CS Programming

1. Programming Basics

   • Variables and constants
     • Variable - is a value that can change during the running of a computer program
       • e.g. SET Num TO 65 SET Num TO Num +1
     • Assignment - this is how a variable or constant is set at the start of the code or at some point within the code
     • Constant - is a value that does not change during the running of a computer program
     • http://www.teach-ict.com/2016/GCSE_Computing/OCR_J276/2_2_programming_techniques/variables_etc/miniweb/index.php
   • Arithmetic operators
     • They are used to combine statements which can be evaluated as T or F
   • Relational operators
     • Are used to compare different items of data within an algorithm
     • For Comparing string you would use 'Hello'
   • Logical operators
     • BIDMAS is needed to create a correct order of operations in a calculation (this could help you find errors within the code
     • are used in algorithms to specify how values are to be used

2. Selection

   • This shows a decision or use of an IF statement within the code
   • Flow chart example
   • Pseudocode example

3. Iteration

   • Determinate loop
     • Count controlled - This is where you know how many time the loop need to run ( For loop's)
   • indeterminate loop
     • Condition controlled, when you do not know how may time the program will loop (while Loop)
   • This is when the program is repeated using loops.

4. Data types

   • Examples
     • Integer - whole number e.g. 34
     • Real - A Decimal number e.g. 13.32
     • Boolean - True or False
     • Character - A single letter e.g. A
     • string - A collection of characters e.g. Hello
   • Declaring Data types
     • Data types may need to be declared within a program. e.g. RECEIVE NAME FROM (STRING) KEYBOARD

5. String Manipulation

   • string traversal - this is the process of moving through a sting one letter at a time, with the use of a loop
     • Length function - can be used to find how may letters are in a string
   • Concatemntaion - this is how to join strings together using the & symbol
   • Indexes - this can display 1 character for a string suing indexing, this starts at 0 for the first letter

6. Arrays

   • Indexes
     • An element is an item of data at a specified index position
   • Tow-dimensional Arrays
     • This is where you have multiple arrays in one array, which forms a matrix(table) structure.
   • Records
     • A collection of data which can be different data types
       • Array of Records e.g. SET name TO ["bob","Dave","Sam"]
   • structure, a way of storing data. This is similar ro a variable but can store multiple data items
     • e.g. SET name TO ["bob","Dave","Sam"]
   • https://www.bbc.com/education/guides/z4tf9j6/revision

7. File Handling

   • Writing to a text file - This uses WRITE method to write data directly to a file or a loop to indirectly write data to the file
   • Reading data from a text file - Each READ statement reads a record from the file into the program and put the data into the Array (for a 2D array the data will need to be split)

8. Subprograms

   • Procedures
     • Do not resturn a value to the main program.
   • Function
     • Return a value to the main program
   • A subprogram is a self contained sequence of program instructions that do a specific task
     • Make the program code easy to read and write
     • Easy to identify errors within the code
     • Make testing easier
     • Makes the program shorter and can code can be reused many times
   • Calling Sub programs -
     • Sub programs are called from within the main program
       • SET name TO getname(name)
   • Local and global Variables
     • Local - can only be used within a subprogram
     • Global - can be used within any subprogram but must be declared at the start of the program

9. Validation

   • This process checks that data that is inputted is correct for the program and meet the data needed for the program to work.
     • Needed to identify unexpected or erroneous data without breaking the program.
   • Presence check - to ensure data has been entered
   • Range check - data should be entered between a range e.g. between 10 and 20
   • Length check - a specified length of number or characters have been entered

10. Testing

    • This is needed to make sure the program meets the needs of the user.
    • Test data
      • Normal data - this is a Valid or in range test
      • Boundary Data - test under extreme conditions e.g. at the upper and lower limits of what to be entered
      • Erroneous data - data that should be be excepted within the code
    • Test plan
      • show the test data, expected and actual results and the type of test
    • Errors
      • Syntax
      • Logical
      • Run time
    • Debugging - the process of identifying errors and correcting them within the code.

11. https://www.bbc.com/education/guides/zrxncdm/revision

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